During the transfer of a volatile liquid such as gasoline or a similar fuel from a storage facility, there is normally an unsealed connection made between the disconnectable nozzle and the tank being filled. As the transfer operation progresses, residual gases contained in the tank, as well as air, normally rise into the atmosphere.
Many municipalities and governmental agencies have proposed or adopted regulations intended to reduce or at least control these emissions. One method toward complying with mandated regulations is the provision of a completely closed system between the fuel source or storage facility and the tank being filled.
Such a closed system normally includes a conduit which carries fuel, to the remote end of which a manually operated dispensing nozzle is attached. The latter is adapted to be removably positioned in the filler pipe of the receiving tank, and includes means to form a sealed engagement between the nozzle spout and the tank filler tube.
Also in many instances, the system is not closed but rather is vented to the atmosphere. With such an arrangement, as liquid is pumped out either of two eventualities could occur. If fuel leaving the system is not immediately replaced by vapor from the tank being filled, air will be drawn into the system. On the other hand, when excessive vapors are drawn in from the tank being filled, some will have to be vented.
Several embodiments of sealing arrangements have been found to be advantageous for providing the necessary vapor tight, yet disconnectable connection at the nozzle spout. One method for providing the desired seal, is to attach a cylindrical, flexible walled member such as a rubber boot or the like, to the fuel dispensing nozzle. The boot in such a position will substantially surround the nozzle spout when the latter is in place. By use of such an arrangement, when the nozzle is received in the filler pipe of the receiving tank, the walls of the flexible boot will be deflected and/or distorted. The boot will thereby define an annular vapor passage while the resilient contact edge thereof sealably engages the tank filler pipe.
This type of arrangement has generally been found to be highly effective. Thus, when a fuel flow is introduced from the nozzle into the receiving tank, a slight pressure is produced within the tank to displace fuel vapors as well as air. These vapors will be urged upwardly through the annulus defined by the nozzle spout and the flexible member. Said vapors can then be transferred by way of the dispensing nozzle through a separate conduit to the fuel source, or to another reservoir for retaining the vapors.
The effectiveness of this system depends to a large degree on the mechanical compatibility of the vehicle with the nozzle, to permit a tight seal at their interface. If for any reason the contact edge of the nozzle boot cannot engage the filler pipe, a seal cannot be achieved, and a leak will result or develop.
Another potential source of vapor leakage is through the above noted tank vents, which are present on some vehicles, particularly those manufactured prior to 1971. When a leak path does develop, some of the vapor from the tank can be emitted to the atmosphere.
In conjunction with closed fuel systems, vacuum assist means have been devised which cause the vapor collection system to operate under a slight vacuum. This tends to pull air into the system through any leak paths which exist or develop. It also tends to inhibit the flow of vapor to the atmosphere. Vacuum assist facilities however often embody the disadvantage of bringing in excessive amounts of air which could produce an undesired mixture in the vapor space. Further, they could produce excessive vent pipe emissons due to the saturation of the excess air as it passes through the system in contact with gasoline.
In the presently disclosed arrangement, a system is provided which incorporates a number of features which include (1) a tight seal at the vehicle-nozzle interface for those vehicles which permit it, (2) a vacuum assist device adapted to aid in collecting vapors from those vehicles which cannot be sealed, (3) the use of a positive displacement hydraulic motor which is driven by the dispensed gasoline flow. Said motor drives a positive displacement vapor pump thereby controlling the volume of vapor pumped in relation to the volume of gasoline dispensed and further limiting the pumping period to the interval when gasoline is being dispensed, and (4) a valved bypass conduit which limits the build-up of a positive or negative pressure, which can be imposed on the vapor space between the vehicle tank and the vapor pump.
Toward assuring the operation of the overall system under varying circumstances, a valved bypass conduit is provided across the positive displacement vapor pump to bypass vapors either to or from the pump suction side.
An object of the invention therefore is to provide a fuel system which embodies an effective sealing means disposed between the fuel dispensing nozzle and a receiving tank. A further object is to provide a balanced fuel system of the type contemplated which is enhanced in response to the inflow of fuel to the receiving tank. A still further object is to provide a vacuum assist arrangement within a fuel system having a dispensing nozzle, which assistance is adjusted in response to the flow of gasoline to the tank and to the volume of vapor which is displaced from the tank during the operation.